Sl'PLEI\) ENTO AI, \OU'!\)EN 21 )SSN: 0210-8984 (Fecha de pulJlicaci6n: 28 de fl'llreru de 1997
BOLETjN DE LA ASOCIACION
ESPANOLA DE ENTOMOLOGiA
Proceedillgs from the 6th European
Workshop
011 JIlsects Parasitoids
Valencia. 1-4
March
1997
Salamanca 1997
nO/II -,!soc <'S/I. ,",/II . SlIpl V (11 2 I I W!7 ISSN 0210-8984
Biology of
Tricltogranlnta cordllbellsis
(Hym.,
Trichogrammatidae) under different photoperiods
P. Gllrcill & .J. TllvaresABSTRACT
This work was carried OUI 10 sludy Ihe efTecl of pholoperiod on Trichofi/'amma
cordl/hellSis Vargas & Cabello biology.
r
cordllhell.lis was reared on r~phestia klle}l1IiellaZeller eggs al 20°C and 7S±S% of HR The essay comprised differenl pholophase (l)
scolophase (D) combinalions Ihal simulaled Ihe day lenglh of summer (16:8), winler (8: 16)
and spring or aulumn (12 12) seasons in Ihe Azores. Pholoperiod did not influence Ihe
parasiloid longevily. emergence rale and parasilism. However, il had a significanl effeci on
Ihe parasiloid egg 10 adult developmenlal lime. Ihe lasl enlarging wilh increasing
pholopilase.
Key-words: I nsecla. Jl-ichogra1l1111o. parasiloid, pholoperiod, biology
INTRODUCTION
The annyworm, Myth;mlla l//IIjJ/lllcta Haworth (Lep .. Noctuidae). is an important pest of the Azorean pastures (T A V ARES. 1989; T A V ARES et al.. 1992). Its high representation has prompted the investigation of various biological control agents, including parasitoids. As part of this research. the evaluation of the native species
{l'ichoKramma cordl/hells;s VARGAS & CABELLO (Hym., Trichogrammatidae)
effectiveness as biological control agent has been oriented towards studying the parasitoid biology (PINTO & TAVARES. 1991; GARCiA & TAVARES, 1995), its population dynamics (GARCIA et 01., 1995) and rearing techniques (TAVARES &
VIEI RA, 1992). Therefore. the present study was desib'Tled to test the effects of different photoperiods on the biology of 7: c()l'dllhcllsis.
18 P (i;Irua &-.1 1:1, :I(C\
\IO\TI:'RL\L ,\1\[) ~IFlIIO[)S
The population of I. mrdllhl'JI.Ils used In this studv was established fillm field-collected par~sitized eggs in Rilleira do (iuiIlH:rme (\zores). ~nd reared Oil eggs of l:fihcslI<I kllehlllellll ZEI.LFR ([.ep .. I'yralidael (I/\\'.'\RI~S 8: \·IUIC\.
19(2)
The effects of three different photophase (L) scotophase ([) combinillions on fecundity (number of host eggs that turned black after parasitization). longe\ity. egg-adult developmental time and adult enlergence of I. c(lrdllhclIsis were determined. These light:dark combinations simulated the da\ length of sunllner (16:8), winter (8: 16) and spring or autulJln (12.12) seasons in the Azores .. \11 treatments were held in bioclimatic chambers at 2()±0.5°C with R.II. of 70±5° o.
For each photoperiod. 40 females with less than 24 hours were individually isolated in glass tubes (7x I cm) containing a card with 200± I 0.7 eggs of E.
kuehnlella and a drop of honey for feed. The host eggs had less them 24 hours and
had been previously inadiated with ultra-violet fOi 20 llIinutes. The egg. cards were daily replaced by fresh ones, and parasitized eggs were allowed to develop ill the same conditions of its parents.
The number of parasitized eggs was counted (hatched and not hatched). as well as the number of hatched offspring The number of dead females was daily observed.
An analysis of variance (ANOVA) was conducted. When statistic;]1 differences existed between data sets (p<0.05). a Schefte test was lIsed to separate the differing means. Data were transfolllled by \/(x+0.5) or arcsin-Jx to reduce variance differences (ZHAR. 19(6)
RESULTS AND DISCUSSION
Fecundity was not significantly affected by the different photophase:scotophase combinations. However. the highest fecundity was observed for 12L 12D. and the lowest for 8L 16D (Table '1 )
I(,L:IID 12L: 12:0 IIL:I(,D
Fecuntlit~· n6±ll.2 75X±2(;X 7U±HI
Lon~e\'il~' (t1a~s) 11.(,±6.5 21 (J±XU 215±~<)
De\'clopmenl(t1a~'s) 1 '.I. HO.7 J IXA±(J.(, a 17.2±(U a
Emergence ("!o) <)X.c,±IA <IX (Ji 1<) <!7.I±.'A
ML'ans ill III..:: S;'I!UL' ro\\ Itlllo\\\!J h~ IhL' ~fI\(' It.:lkr <In.: :-:ig.nil'I(,lIIlh Jill\:r..:nf I S(,:hdl'L'
10
Table I \kant<:;(andaru dC\I;!tIlHl or Ih(' fl'nIllU!I~ (110 of para<:;llll.(,u cg.g" Ix'r "[cllwkl. IOI1g.l'\i[~
UC\l'I0pllIl'lIlal II 11K' ;mu ;Iuliit CllIcrgC!lI.:c rall'~ or I {"1I/"dllhl'fI.".\ IInder llllTcrclH
phOl0f1h~I<:;(,· scn[oplw,(' (oillhi 11;11101\<:;
['arasillsm \\as highL'r ill Ihe IIrSI dm alter l'lllL'rgellce. \\ith nil ilverilge or I.JX+7C, (16LXI». 17XHC, (121.121» nllu 15.:>r7.5 (SIS\)) pmnsiti7.ed eggs per female III Ihe second dn\. the Illllnlin of pnrasitizl'u eggs SllOngl~· ul'eiJlled. alld in the rollo"illg. dn\·s. these \allies tellded 10 uecreilse IO\\·ilrds nro. HllllOUg.h wilh oseillHting \·allies alollg. Ihe lime. regnruless tlil' photophase length (Figme 1 .\. fl.
o
:w
9J 1\
- M ~') 1- oY> :: ::l !':1 ~ 9 :; Si fl ". ""I ;:::
I)"),,
Figurc I r>.lcalllllllllOCf ofpafaslli/cLi eggs IJo.:f feillale 1---1 allLl Lla;h <leCulllul:II;,·C paras;l;sm I) of I.
SOIllC authors have shown that thc fccundity is not influcnced by pho~ophasc length (CALVIN 1'/ (II., 198<t: n)NSOLI 8.:. PARRA. 1994). llow\.:vcr. 7.'\SI..·\ \'SKI & KVI (1982) verified that hoth In
r
('\'III1£'IC£'1I1' and 'I: chi/(}lIil', the numher of eggs lAid by progeny females depends on the length of the photophase in the this generation.Regarding accumulative parasitislll. this was more rcle\ant in the first w'eek reaching more than <to% of the parasitized eggs. for all photophase lengths
For I: COrdllh£'llsil, photophase had no significant effect on parasitoid's
longevity (Table I) C.L\L VI N 1'/ al. (198<t). concluded that the photophase length influenced the females longevity of Fric/wgra/ll/l1(/ ['IT/WI/IIII. but it did not had a significant effect on the males longevity. However. these authors observed that there appeared to be a trend of higher longevity with an increased pbotophase. in both sexes On the contrary. CONSOLI &. P,,\RRA (1994). concluded that 1'. gu II(} I females life span decreased with an increase in photoplrase. These contradictOlY results suggest that the photoperiod influence on the parasitoid longevity probably depends of each species ecological adaptations to their natural habitat.
No significant differences were found between all photophase:scotophase combinations for
7:
('()rdllhl'lIl'js emergence rates (Table I). Similar results were obtained by CONSOLI & PARR,", (1994) for 1'. gall(}i.In egg parasitoids. several species are kno\vn to respond either to temperature or photoperiod as cues for timing the induction of diapause (VOEGELE 1'/ (1/ ..
1986: LAING & CORRIGAN. 1995) In Jric!lIIgral1ll11(1 emIlL'scem, photoperiod acts most lyon the adults while temperature is the most important factor for the developing larva and. together these iwo factors detennine the induction of diapause (ZASLA VSK Y & UMAROVA. 1982). CAL VIN ('/ a/ ( 1984) verified that with decreasing photophase there was an increase on developmental time of
l'ric/lllgral1lnw [,re/i(}slIn!, possibly related with parasitoids quiescence. For
1:
cordI/hens is, developmental time was the only parameter that was significantly
influenced by photophase length (ANOVA, F=5838. p<O.OOO I). However. for thi~ species. as day length increased. developmental time enlarged. A possible expla/lation for this may relay on the emergence rhythms of I. c(lrdl/h('//I'is.
Assuming that most of the adults of this species emerge during the scotophase. some parasitoids would have to delay the emergence to the ne.xt scotophase when the last is short (and day length'is long). this way enlarging the' developmental time. ACKNOWLEDGEMENTS
Financial support for this work was provided by the llniversidade dos A\ores, Funda\ao Luso-Americana para 0 Desenvolvimento and Secretaria Regional de Agricultura e Pescas.
21
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